Process for the production of a pourable phosphate-free foam-inhibiting preparation

ABSTRACT

A process for the production of pourable foam inhibitor granules comprising forming an aqueous solution of a mixture of an alkali metal carboxymethyl cellulose and a nonionic cellulose ether and maintaining the aqueous solution at slightly elevated temperature until the viscosity is at least 60% of the viscosity obtained by complete swelling of the solution, adding a water insoluble foam inhibitor and a phosphate-free mixture of at least two of an alkali metal silicate, an alkali metal carbonate and an alkali metal sulfate into the aqueous mixture which is then spray-dried to form the pourable foam inhibitor granules. 
     The invention also relates to the pourable foam inhibitor granules produced by the above process.

This invention relates to a process for the production of a granularfoam-inhibiting preparation containing a foam-inhibiting agent, a solidphosphate-free carrier material and a cellulose ether mixture.

DE 23 38 468 A1 (US-A-3,933,672) relates to a detergent containing asilicone foam inhibitor which is protected against interaction withsurface-active ingredients of the detergent. For its production, aqueousmelts containing the silicone foam inhibitor and a carrier impermeableto surfactants, such as polyglycols or highly ethoxylated alkylpolyglycol ethers, are first spray-dried and the particles obtained aresubsequently provided with a coating in a fluidized bed. Salts typicallyused in detergents, more particularly tripolyphosphate or carboxymethylcellulose, may be used as the coating material. A multistage productionprocess such as this is relatively complicated. In addition, thephosphate content is problematical. It has also been found that theshell material only releases the foam inhibitor with delay at lowwashing temperatures and the undissolved particles can become caught upin the washing where they can cause greasy stains.

DE 31 28 631 - A1 describes the production of foam-inhibited detergentscontaining microencapsulated silicone foam inhibitors. The silicone isdispersed in an aqueous solution of a film-forming polymer and thedispersion is delivered to the spray-drying tower through a separatepipe, i.e. separately from the other detergent ingredients dissolved ordispersed in water. The two streams are combined in the spray nozzle.The film-forming polymer may be selected, for example, from celluloseethers, starch ethers or synthetic water-soluble polymers and mixturesthereof. The microcapsules are formed spontaneously in the spray nozzleor by preliminary precipitation by addition of electrolyte salts to thesilicone dispersion. The described process is confined to the productionof spray-dried detergents and cannot be applied to detergents andcleaning preparations produced by other methods, for example bygranulation, or even in other fields of application.

EP 97 867 - A2 describes a process for the production ofmicroencapsulated foam-inhibiting oils by mixing of a silicone emulsionwith an aqueous solution of carboxymethyl cellulose and precipitation ofthe microcapsules by addition of electrolytes, more particularlypolyvalent salts, or organic solvents. It has been found that theproduction of the silicone dispersion requires the presence of non-ionicsurfactants having an emulsifying effect. However, this addition leadsto a distinct reduction in foam-inhibiting activity. In addition,considerable difficulties are involved in homogeneously dispersing thesmall quantities of silicone microcapules required for adequate foaminhibition in a comparatively large quantity of washing powder. Inaddition, the continuous mixing process is complicated by electrostaticcharging of the particles in the transport and metering units.

DE-A-34 36 194 - A1 describes a process for the production of pourablefoam-inhibiting granules by spray-drying of an aqueous foam-inhibitingdispersion containing film-forming polymers. To produce granulesconsisting of

a) 1 to 10% by weight water-insoluble foam inhibitor,

b) 0.2 to 2% by weight of a mixture of sodium carboxymethyl celluloseand methyl cellulose in a ratio by weight of 80:20 to 40:60,

c) 70 to 90% by weight inorganic carrier salts soluble or dispersible inwater,

d) balance water,

an aqueous solution containing 0.5 to 8% by weight of the celluloseether mixture (b) is allowed to swell at a temperature of 15° to 60° C.until the viscosity of the solution is at least 75% of the viscositymeasured after complete swelling of the cellulose ether solution, afterwhich the foam inhibitor (a) is dispersed in the solution and thehomogenized dispersion is spray-dried after addition of the carriersalts and, optionally, water.

Organopolysiloxanes, paraffins and mixtures of organopolysiloxanes andparaffins are used as the foam inhibitor. The foam inhibitor content isbetween 1 and 10% by weight and preferably between 3 and 7% by weight.The carrier salt preferably consists of a mixture of sodium silicate,sodium tripolyphosphate and sodium sulfate. The preparation described inthe Example contains (in addition to other ingredients) 5.5% by weightof a silicone foam inhibitor and 31.5% by weight sodiumtripolyphosphate.

It has now been found that the preparations described in DE-A 34 36 194Al can be considerably improved in their foam-inhibiting effect andecological compatibility by following the teaching according to thepresent invention.

The first problem was to replace the tripolyphosphate in the carriersalt by P-free salts. However, it was found that replacement by sodiumsulfate and/or sodium silicate has an unfavorable effect, particularlywhen relatively large amounts, for example 8% by weight and more, oforganopolysiloxane foam inhibitors are to be incorporated. On the otherhand, it has been found that with increasing content of polysiloxanefoam inhibitors in the granules, their effect increasesoverproportionally in subsequent use. Accordingly, the necessaryquantities of polysiloxanes can be distinctly reduced without any lossof foam-inhibiting activity providing granules having a relatively highcontent of adsorbed polysiloxane foam inhibitors are used. However,where the individual salts or salt mixtures described in DE 34 36 194are used in the absence of phosphates, the flow properties of thegranules deteriorate if the content of polysiloxane foam inhibitor ismore than 7.5% by weight and, in particular, more than 10% by weight. Inthis range, the granules tend to adhere to one another and to exude thepolysiloxane.

The invention described hereinafter avoids these disadvantages andprovides for the production of free-flowing, storable foam inhibitorgranules having a high content of active substance and an improvedfoam-inhibiting effect, based on the quantity of foam inhibitor used.

The present invention relates to a process for the production ofpourable foam inhibitor granules containing

(a) a water-insoluble foam inhibitor from the class ororganopolysiloxanes containing fine-particle silica and mixtures thereofwith paraffin oil and/or paraffin wax,

(b) 0.2 to 3% by weight of a mixture of sodium carboxymethyl celluloseand a nonionic cellulose ether in a ratio by weight of 80:20 to 40:60,

(c) 70 to 90% by weight inorganic carrier salts soluble or dispersiblein water,

(d) balance water,

in which an aqueous solution containing 2 to 8% by weight of thecellulose ether mixture (b) is allowed to swell at a temperature of 15°to 60° C. until the viscosity of the solution is at least 60% of theviscosity measured after complete swelling of the cellulose ethersolution, the foam inhibitor (a) is dispersed in this solution and,after addition of the carrier salts and optionally water, thehomogenized dispersion is spray-dried, characterized in that thepercentage content of component (a) is between 7.5 and 18% by weight andcomponent (c) is phosphate-free and consists of a mixture of sodiumsilicate, sodium carbonate and sodium sulfate.

The foam inhibitor (component a) may be selected from typicalorganopolysiloxanes containing fine-particle silica which may even besilanized. The content of silica or silanized silica in these known foaminhibitors is normally between 0.5 and 10% by weight and mostly between1 and 6% by weight. Mixtures of foam inhibitors such as these withparaffins, such as paraffin oils, soft and hard paraffins andmicrocrystalline paraffin waxes, are also suitable. They may alsocontain silanized silica.

Particularly preferred foam inhibitors are silica-containing dimethylpolysiloxanes and mixtures thereof with foam-inhibiting paraffin waxes,including microparaffin waxes. In mixtures such as these, the percentagecontent of silica-containing polydimethyl siloxanes is preferably atleast 30% by weight and, more preferably, at least 50% by weight of thefoam-inhibiting agent. The content of foam-inhibiting agent in thegranules is between 7.5 and 18% by weight, preferably between 10 and 14%by weight and, more preferably, between 10.1 and 14% by weight.

Component (b) consists of a mixture of (b1) carboxymethyl cellulosesodium salt (CMC) and (b2) at least one compound from the class ofnonionic cellulose ethers. Suitable compounds of this class are methylcellulose, ethyl cellulose and mixed ethers, such as methyl hydroxyethylcellulose, methyl hydroxypropyl cellulose, methyl hydroxybutyl celluloseand ethyl hydroxyethyl cellulose. Methyl cellulose (MC), methylhydroxyethyl cellulose (MHEC) or methyl hydroxypropyl cellulose (MHPC)is preferably used in combination with CMC. The CMC normally has adegree of substitution of 0.5 to 0.9 carboxymethyl groups peranhydroglucose unit. The MC general]y contains 1.2 to 2 methyl groupsper anhydroglucose unit. The MHEC and the MHPC may contain 0.5 to 2methyl groups and 0.05 to 0.8 hydroxyethyl groups per anhydroglucoseunit.

Particularly preferred components (b2) are mixed ethers of methylcellulose containing hydroxyethyl or hydroxypropyl groups which arereferred to in the foregoing by the abbreviations MHEC and MHPC andwhich advantageously contain 1 to 1.8 methyl groups and 0.1 to 0.5hydroxyethyl or hydroxypropyl groups per anhydroglucose unit. Mixturesof CMC and MHEC or of CMC and MHPC are particularly suitable for theproduction of foam inhibitor concentrates having a high active-substancecontent and swell to the required level comparatively quickly.Accordingly, they provide for the production of foam inhibitorpreparations showing overproportionally high foam-inhibiting activity.

The ratio by weight of CMC to nonionic cellulose ethers is 80:20 to40:60, preferably 75:25 to 60:40 and, more preferably, 73:27 to 68:32.These mixing ratios have proved to be particularly favorable for thestability of the aqueous foam inhibitor dispersions intended for spraydrying.

The cellulose ether mixture is preswollen in water before the foaminhibitor is added. Complete swelling of the aqueous cellulose ethersolution takes about 15 to 24 hours at 20° C. and about 1.5 to 4 hoursat 40° C. Before addition of the foam inhibitor, swelling should haveprogressed to such an extent that at least 65% and, more particularly,at least 80% of this final state--reflected in a viscosity maximum--isreached. At a solution temperature of 20° C., the foam inhibitor may beadded after 12 to 24 hours; at a solution temperature of 40° C., it maybe added after 1 to 3 hours. Later addition does not improve thestability of the dispersion significantly, if at all.

The concentrations of the aqueous cellulose ether solution are bestbetween 2 and 8% by weight and preferably between 3 and 6% by weightand, accordingly, are higher on average than proposed in DE 34 36 194which has proved successful in particular with relatively highpolysiloxane contents.

The foam inhibitor (a) is best dispersed by means of effective stirringand mixing units to prevent any tendency towards separation due to thehigh salt concentrations. It has also been found to be useful to heatthe dispersion to temperatures of 50° to 95° C. Where paraffin waxes areused as the foam inhibitor, the temperature should be at least 70° C.Heating of the dispersion produces an increase in viscosity andfacilitates further processing.

The carrier material (component c) consists of a mixture of sodiumsilicate, sodium carbonate and sodium sulfate. Mixtures of 5 to 15% byweight sodium silicate (composition Na₂ O:SiO₂ =1:2 to 1:3.5), 20 to 60%by weight sodium carbonate and 25 to 65% by weight sodium sulfate haveproved to be particularly suitable. These figures are based on thecontent of anhydrous salts in the foam inhibitor granules. Mixtures of7.5 to 13% by weight sodium silicate, 25 to 50% by weight sodiumcarbonate and 30 to 50% by weight sodium sulfate are preferably used.The sodium silicate used preferably has the composition Na₂ O:SiO₂:=1:2.5 to 1:3.3.

The total content of carrier salt in the foam inhibitor granules isbetween 70 and 90% by weight and preferably between 75 and 85% byweight.

The heated homogenized dispersion normally has a water content of 40 to50% by weight and preferably 45 to 48% by weight. It is delivered to atypical spray-drying plant, advantageously with continuoushomogenization, for example by pumping through a ring pipe with ahomogenizer in between, and is spray-dried by means of nozzles in afree-fall zone through which hot drying gases flow. The temperature ofthe drying gas, which preferably flows in countercurrent, is normallybetween 160° and 280° C. at the entrance to the spray-drying tower, theso-called ring duct, and between 70° and 110° C. in the offgas pipebefore entry into the dust filter.

The degree of drying is adjusted in such a way that the water content,including the water of hydration, is generally between 3 and 10% byweight and preferably between 3.5 and 7.5% by weight.

The granules obtained have an apparent density of 650 to 800 g/l and aparticle size distribution comparable with that of typical granulated orspray-dried detergents. With the stated water content, the preparationshows very good pouring and flow properties. The preparation is easy toincorporate in granular detergents and does not separate duringtransport and storage of the mixtures. The foam-suppressing propertiesof the foam inhibitor remain fully intact during processing and also instorage, so that very small quantities of foam inhibitor are sufficient.The solubility of the end products in cold and warm water is comparablewith that of typical granular detergent mixtures, so that there is nodelay in the development of the inhibitor effect in the practicalapplication of the preparations.

Apart from washing and cleaning preparations, the granules may also beused for other applications, for example for the defoaming of pulps,wastewaters, oil emulsions, dye solutions and in chemical processengineering.

EXAMPLES

The sodium carboxymethyl cellulose (CMC) used in the following Examplescontained 0.7 carboxymethyl groups while the methyl cellulose (MC)contained 1.8 methyl groups per anhydroglucose unit. The methylhydroxyethyl cellulose (MHEC) and the methyl hydropropyl cellulose(MHPC) each contained 1.6 methyl groups and 0.2 hydroxyalkyl groups peranhydroglucose unit.

EXAMPLE 1

An aqueous solution containing 4.6% by weight cellulose ether (ratio byweight Na-CMC: MC=70:30) was allowed to swell for 24 hours at 20° C.Instead of a swelling time of 24 hours at 23° C., a swelling time of 2or 4 hours at 40° C. was also sufficient. The viscosity of the swollensolutions was more than 90% of the final viscosity.

160 kg of a polysiloxane foam inhibitor (polydimethyl siloxanecontaining microfine silanized silica) were dispersed in 435 kg of thissolution. After heating to 60° C., the solution was mixed with asolution--also heated to 60° C.--containing 574 kg of a 34.9% by weightwaterglass solution (Na₂ O:SiO₂ =1:3.0), 142 kg water and 814 kg sodiumsulfate (anhydrous). 700 kg sodium carbonate (anhydrous) were thenadded. Under the effect of the heat of solution and hydration released,the temperature rose to around 70° C. The dispersion (water content34.2% by weight) was sprayed through nozzles into a spray-drying towerunder a pressure of 40 bar with continuous homogenization and dried byhot combustion gases flowing in countercurrent (temperature in the ringduct 250° C.; at the tower exit 98° C.). The composition of the endproduct was as follows (% by weight):

    ______________________________________                                        foam inhibitor         8.0%                                                   cellulose ether        1.0%                                                   Na silicate            10.0%                                                  Na sulfate             40.7%                                                  Na carbonate           35.0%                                                  Water                  5.3%                                                   ______________________________________                                    

The particle size of the spray-dried product was between 0.1 and 1.2 mmwith a maximum of 0.5 to 0.7 mm. The weight per liter was 700 g/1. Theproduct showed good flow properties with no dust emission. Afterincorporation in a conventional detergent (0.5 part by Weight product to99.5 parts by weight detergent), no excessive foaming occurred when thedetergent was used in a drum-type washing machine (detergentconcentration 7.5 g/1) whereas a comparison product with no foaminhibitor added overfoamed. Identical foam behavior was observed when amixture of 99 parts by weight detergent and 1 part by weight foaminhibitor granules was used in accordance with Example 2 of DE-A 34 36194 in the content of 5.5% by weight mentioned therein. Accordingly,foam-inhibiting activity was increased by a factor of 1.4.

EXAMPLE 2

An aqueous solution containing 4.6% by weight cellulose ether (ratio byweight of CMC:MHEC=70:30) was allowed to swell for 20 hours at 20° C.Instead of a swelling time of 20 hours at 20° C., a swelling time of 1.5to 3 hours at 40° C. was also sufficient. The viscosity of the swollensolutions was more than 90% of the final viscosity.

As described in Example 1, 204 kg of a polysiloxane foam inhibitor(polydimethyl siloxane containing microfine silanized silica) weredispersed in 435 kg of this solution. After heating to 60° C., thedispersion was mixed with a solution--also heated to 60° C.--containing574 kg of a 34.9% by weight waterglass solution (Na₂ O:SiO₂ =1:3.0), 142kg water and 770 kg sodium sulfate (anhydrous). 700 kg sodium carbonate(anhydrous) were then added. Under the effect of the heat of solutionand hydration released, the temperature rose to around 70° C. Thedispersion (water content 34.2% by weight) was sprayed through nozzlesinto a spray-drying tower under a pressure of 40 bar with continuoushomogenization and was dried with hot combustion gases flowing incountercurrent (temperature in the ring duct 250° C.; at the tower exit98° C.). The composition of the end product is as follows (% by weight):

    ______________________________________                                        foam inhibitor         10.2%                                                  cellulose ether        1.0%                                                   Na silicate            10.0%                                                  Na sulfate             38.2%                                                  Na carbonate           34.8%                                                  Water                  5.8%                                                   ______________________________________                                    

The particle size of the spray-dried product was between 0.1 and 1.2 mmwith a maximum of 0.5 to 0.7 mm. The weight per liter was 710 g/l. Theproduct showed good flow properties with no dust emission. Afterincorporation in a conventional detergent (0.3 part by weight product to99.7 parts by weight detergent), only moderate foaming occurred when thedetergent was used in a drum-type washing machine (detergentconcentration 7.5 g/l). Identical foam behavior was observed when amixture of 98.7 parts by weight detergent and part by weight foaminhibitor granules was used in accordance with Example 2 of DE-A 34 36194 in the content of 5.5% by weight mentioned therein. Accordingly,foam-inhibiting activity was increased by a factor of 1.8.

EXAMPLE 3

As described in Example 1, a foam inhibitor consisting of polydimethylsiloxane and silanized silica is dispersed in a swollen solutioncontaining 5% by weight of a mixture of 72 parts by weight Na-CMC and 28parts MHPC. After addition of aqueous Na silicate solution (Na₂ O:SiO₂=1:3.0, water content 65.1% by weight), sodium sulfate, sodium carbonateand water, a slurry (temperature 75° C.) having the followingcomposition (in % by weight) was obtained:

    ______________________________________                                        foam inhibitor         8.5%                                                   cellulose ether        0.8%                                                   Na silicate            7.5%                                                   Na sulfate             28.0%                                                  Na carbonate           21.3%                                                  Water                  33.9%                                                  ______________________________________                                    

After homogenization and spray drying (temperature of the heating gas atthe tower entrance 260° C.; at the tower exit 99° C.), free-flowinggranules having an apparent density of 720 g/l and the followingcomposition (in % by weight) were obtained:

    ______________________________________                                        foam inhibitor         12.0%                                                  cellulose ether        1.1%                                                   Na silicate            10.6%                                                  Na sulfate             39.5%                                                  Na carbonate           30.1%                                                  Water                  6.7%                                                   ______________________________________                                    

Compared with the composition product according to DE-A 34 36 194, foaminhibiting activity is higher by a factor of 2 for identical quantitiesof polysiloxane foam inhibitor.

What is claimed is:
 1. A process for the production of phosphate-free pourable foam inhibitor granules comprising the steps of:A) forming an aqueous solution containing from about 2 to about 8% by weight of a mixture of cellulose material, wherein said mixture of cellulose material consists of sodium carboxymethyl cellulose and at least one nonionic cellulose ether in a ratio of weight of about 80:20 to about 40:60; B) maintaining the aqueous solution formed in step A) at a temperature in the range of from about 15° to about 60° C. until the viscosity of the solution is at least about 60% of the viscosity obtained by complete swelling of the solution; C) dispersing in the solution from step B), optionally with the addition of water, the following:(a) a water-insoluble foam inhibitor consisting essentially of either;(i) at least one organopolysiloxane containing fine particle silica, or (ii) at least one organopolysiloxane containing fine particle silica in admixture with at least one of paraffin oil and paraffin wax; and (b) a phosphate-free carrier material mixture comprised of from about 5 to about 15% by weight of sodium silicate having the composition Na₂ O:SiO₂ such that the ratio of Na₂ O to SiO₂ is from about 1:2 to about 1:3.5, from about 25 to about 60% by weight of sodium carbonate, and from about 25 to about 65% by weight of sodium sulfate, wherein the above percentages are based on the anhydrous salts relative to the total weight of said phosphate-free carrier material mixture; and D) spray-drying the dispersion resulting from step c) to form said phosphate-free pourable foam inhibitor granules, wherein said pourable foam inhibitor granules contain from 10.1 to about 18% by weight of said water-insoluble foam inhibitor; from about 0.2 to about 3% of said cellulose material, and from about 70 to about 90% by weight of said carrier material mixture, relative to the total weight of said phosphate-free foam inhibitor granules.
 2. The process of claim 1 wherein step C) further comprises the step of heating the dispersion formed therein to a temperature of from about 50° to about 95° C. prior to carrying out step D).
 3. The process of claim 2 wherein said phosphate-free foam inhibitor granules contain from about 3 to about 10% by weight of water.
 4. The process of claim 3 wherein said phosphate-free foam inhibitor granules contain from about 3.5 to about 7.5% by weight of water.
 5. The process of claim 1 wherein said organopolysiloxane is polydimethyl siloxane.
 6. The process of claim 5 wherein said fine particle silica in step C) (a) is silanized silica.
 7. The process of claim 1 wherein step C) is carried out by the dispersion of said water-insoluble foam inhibitor followed by the dispersion or solution of said phosphate-free carrier material mixture.
 8. The process of claim 1 wherein said phosphate-free carrier material mixture comprises from about 7.5 to about 13% by weight of sodium silicate having the composition Na₂ O:SiO₂ such that the ratio of Na₂ O to SiO₂ is from about 1:2.5 to about 1:3.3, from about 25 to about 50% by weight of sodium carbonate, and from about 30 to about 50% by weight of sodium sulfate; wherein the above percentages are based on the anhydrous salts relative to the total weight of said phosphate-free carrier material mixture.
 9. The process of claim 1 wherein in step A) said nonionic cellulose ether is at least one of methyl cellulose, methyl hydroxyethyl cellulose, and methyl hydroxypropyl cellulose in a ratio by weight of sodium carboxymethyl cellulose to said nonionic cellulose ether of from about 75:25 to about 50:50.
 10. The process of claim 1 wherein said aqueous solution of step A) contains from about 3 to about 6 grams per liter of said mixture of cellulose material.
 11. The phosphate-free pourable foam inhibitor granules produced by the process of claim
 1. 12. The process of claim 1 wherein in step D) the pourable foam inhibitor granules contain from 10.1 to about 14% by weight of said water-insoluble foam inhibitor.
 13. Phosphate-free pourable foam inhibitor granules consisting essentially of:(a) from 10.1 to about 18% by weight of a water-insoluble foam inhibitor containing either(i) at least one organopolysiloxane containing fine particle silica, or (ii) at least one organopolysiloxane containing fine particle silica in admixture with at least one of paraffin oil and paraffin wax; (b) from about 0.2 to about 3% by weight of a mixture of sodium carboxymethyl cellulose and at least one nonionic cellulose and at least one nonionic cellulose ether in a ratio by weight of about 80:20 to about 40:60; and (c) from about 70 to about 90% by weight of a phosphate-free carrier material mixture comprising from about 5 to about 15% by weight of sodium silicate having the composition Na₂ O:SiO₂ such that the ratio of Na₂ O to SiO₂ is from about 1:2 to about 1:3.5, from about 25 to about 60% by weight of sodium carbonate, from about 25 to about 65% by weight of sodium sulfate, wherein the above percentages are based on the anhydrous salts relative to the total weight of said phosphate-free carrier material mixture.
 14. The phosphate-free pourable foam inhibitor granules of claim 13 wherein in component (a) the organopolysiloxane is polydimethyl siloxane.
 15. The phosphate-free pourable foam inhibitor granules of claim 14 wherein said nonionic cellulose ether in component (b) is at least one of methyl cellulose, methyl hydroxyethyl cellulose, and methyl hydroxypropyl cellulose, in a ratio by weight of said sodium carboxymethyl cellulose to said nonionic cellulose ether of from about 75:25 to about 50:50; and wherein said phosphate-free carrier material mixture comprises from about 7.5 to about 13% by weight of sodium silicate having the composition Na₂ O:SiO₂ such that the ratio of Na₂ O to SiO₂ is from about 1:2.5 to about 1:3.3, from about 25 to about 50% by weight of sodium carbonate, and from about 30 to about 50% by weight of sodium sulfate; wherein the above percentages are based on the anhydrous salts relative to the total weight of said phosphate-free carrier material mixture.
 16. The phosphate-free pourable foam inhibitor granules of claim 13 wherein in component (a) from 10:1 to about 14% by weight of water-insoluble foam inhibitor is present in the granules. 